All the male employees of the Italian Railroad system at work on April 1st 1963 have been classified by age, occupation, level of physical activity and some other social and working characteristics. Such cohort for a total of over 172,000 men has been followed for 5 years for all retirements and deaths. The first 5 year analysis, concerned with relationship of physical activity with death, has shown that deaths for myocardial infraction and sudden coronary death are more frequent in sedentary and moderatly active people as compared with heavy workers. No substancial differences were found for cancer and stroke deaths; whereas death rates due to other degenerative (non coronory) heart disease, for chronic bronchitis and violence were higher in heavy workers as compared with the others. The present project intends to throw a better light on the relationship of habitual physical activity at work with causes of death and mainly with coronary heart disease, by enlarging the study along a 10 year follow-up of the same initial cohort. Plans have been made for comparing such 10 years data with similar data collected by Dr Henry L. Taylor for the University of Minnesota, in samples of American Rail Road Employees. Dr. Taylor has been consultant to this study since its early planning.